Solidification Pressure Research Articles

Comments on "Evidence for a New Phase of SolidHe3"

The interpretation of Osheroff, Richardson, and Lee of their recent measurements of the solidification pressure of ${\mathrm{He}}^{3}$ is reexamined. On the basis of a different assumption about the thermal coupling in the solid, it is concluded that the transition is unlikely to be of first order and is more likely the expected $\ensuremath{\lambda}$ transition to the ordered antiferromagnetic phase.

Neutron Scattering by Rotons in Liquid Helium

The elementary excitations in superfluid helium have been studied in the wave-vector range $1.5<Q<2.3$ ${\mathrm{\AA{}}}^{\ensuremath{-}1}$ by inelastic neutron scattering. The single-excitation scattering function ${\mathcal{S}}_{1} (Q, \ensuremath{\hbar}\ensuremath{\omega})$ was measured for pressures between 1 atm and the solidification pressure and for temperatures from 1.3\ifmmode^\circ\else\textdegree\fi{}K to above the transition temperature ${T}_{\ensuremath{\lambda}}$. The dispersion curves were fitted to parabolas and the appropriate Landau parameters tabulated vs temperature and pressure. By accounting for the effect of the instrumental resolution it was possible to observe a line broadening at low temperatures which sets in when the slope of the dispersion curve equals the sound velocity. There are strong indications that this is due to the roton-phonon interaction proposed by Pitaevskii. The line broadening observed when the temperature approaches ${T}_{\ensuremath{\lambda}}$ is well accounted for by the roton-roton interaction as calculated by Landau and Khalatnikov. The results have been related through thermodynamics to other properties of the liquid and the spectral form of the excitations compared to those observed in magnetic systems close to the critical temperature.

The Crystallization of Neutronic Matter

Solidification pressure PS of neutron matter has been estimated on the basis of the quantum mechanical principle of corresponding states, using density dependent characteristic reduction parameters derived from a realistic twonucleon interaction. Three procedures yield Ps¯≈ 5 × 1027 atm, in essential agreement with an earlier estimate1.

Solidification Pressure of Nuclear and Neutron Star Matter

LITTLE attention seems to have been paid to the possibility of a neutron solid—a solid lattice of neutrons—or to consideration of the density regime in which it might exist. A useful theoretical calculation would be prohibitively complicated, so we have adopted an empirical approach based on scaling the properties of helium and other substances with a corresponding states argument. We are able to predict a solidification pressure for neutron matter and suggest modifications to the equation of state.

The relation between the fatique strength and the gas content of Lo-Ex

The object of this work was to investigate the relation between fatigue strength and number of pin-holes of metal specimens (the latter depended upon the gas content of the molten metal). The specimens were prepared from molten Lo-Ex having various contents of gas, which had been determined by reduced pressure solidification test. The number of pin-holes was counted by improved color check test. In the fatigue test, the number of cycles before rupture under ±12kg/mm2 of repeated tension and compression stress was counted with Vibrophore type machine.The results obtained were summarized as follows.(1) When the gas content in the molten alloy increased, the number of pin holes on the surface of the specimen increased and the fatigue strength remarkably decreased; whereas, the tensile strength was scarcely affected by the gas content.(2) The fatigue strength was high when the specimen had only a few (not more than 3-4/cm2) pin-holes and the majority (more than 1/2) of such specimens represented endurance limit of over 107 cycles.(3) The fatigue strength remarkably decreased when the specimen had many (not less than about 4/cm2) pin-holes and very few of such specimens represented endurance limit of over 107 cycles.(4) When the endurance limit was not over 107 cycles, the relation between the endurance limit and the number of pin-holes was approximately expressed by a logarithmic linear function.(5) In the practical work of melting and casting, it was found that fluxes containing moisture reduced fatigue strength owing to the increase of gas content in the molten metal.

X-ray and optical studies of GaAsx- P1-x crystals : S.A. Abagyan, S.M. Goridetsky and T.B. Jukova (Vol. 7, No. 1, pp. 200–206.

Hydrostaticity of poly(methyl methacrylate) (PMMA) loaded in a diamond anvil cell (DAC) was investigated up to ∼10 GPa under two conditions, i.e., with and without pressure-transmitting medium. When PMMA was loaded in the DAC without methanol-ethanol mixture, one of the most widely-used pressure-transmitting media, hydrostatic pressure condition was not fulfilled having a pressure gradient. However, the Brillouin frequency shift of the longitudinal acoustic mode of PMMA exhibited nearly the same pressure dependence regardless of the loading condition whether it was loaded with or without the methanol-ethanol mixture. This suggests that the equation of state (pressure-density relationship) of PMMA, which is calculated by using the Brillouin frequency shift, can be obtained reliably without any pressure medium at pressures less than the solidification pressure of the liquid.

The heat conductivity and viscosity of liquid helium II

Measurements have been made in glass capillary tubes of 52 and 108 u diameter, in the temperature range from 1.15 to 2.15 °K. For sufficiently small temperature gradients the thermal resistance is independent of the heat flow and is caused solely by the viscosity of the normal fluid, n n . This viscosity has been calculated from the measured thermal resistance data with the use of the existing entropy values, and the results from the two tubes are in very good agreement except for a small deviation at low temperatures which is attributed to slip. The viscosity at the saturated vapour pressure, when corrected for slip, agrees closely with the results obtained by the rotating cylinder viscometer but does not agree with the oscillating disk experiments. The variation of n n at low temperatures follows the theory of Landau & Khalatnikov if A/ k is taken as 8.9 °K, but the measured values of the slip correction are slightly larger than would be expected from the theoretical phonon and roton mean free paths. In the 52 u tube the measurements have been extended up to the solidification pressure so as to give n n as a function of density. Near the lambda line n n increases rapidly with density, but at low temperatures the variation is quite small and it is found that the contribution from the rotons is almost independent of density.